Shredder type hammermill



O United States Patent [1113,545,690

[72] Inventors Weneil J. Burials; 3,326,478 6/1967 Van Endert 241/186Donald E. Herman; Robert M. Stepanek; 3,335,967 8/1967 Williams...IOU/97X Paul R. Vilian, Cedar Rapids, Iowa 3,426,674 2/1969 Testolin100/95 1966 Primary Examiner-William S. Lawson [45] Pa Dec. 1970Attorney Darbo, Robertson and Vandenburgh [73] Assignee PettiboneCorporation Chicaimmlm ABSTRACT In a shredder r or car bodies the bodiesare fed a corporation of Delaware over a notched cutter bar. A rotor hasswing hammers of two lengths, one set passing through the notches andthe other [54] SHREDDER TYPE HAMMERMILL passing close to the teethbetween the notches. Just beyond the cutter bar spaced bars and inwardprojections cooperate 13 Claims, 7 Drawing Figs.

to let bnttie material escape. Beyond these, escape of frag- [52] U.S.Cl. 241/186, mem is aided by sloping the sides of the bars which theywill 3 241/190 241/193 241/194 241/285 strike outwardly and in thedirection of movement. The bodies [5 l] int. Cl. ..B02c 13/04, are feddown a chute with feed controlled by a driven toothed B02: 13/286 rollerwhich can move up and downwardly, being carried by a [50] Field olSearch241/186, frame that is remotely pivotecL The rear upper portion of the189, 190, 193, 194, 285, 295; lQ0/94- housing for the hammermill is ahood hinged at its rear edge and swinging past a balanced position.Hydraulic cylinder [56] References Cited means are provided for thefeeder and the hood each double- UNITED STATES PATENTS acting. A jointhydraulic system is provided with separate 2,655,213 53 Anderson 4 /29manual valves for the two functions and a selector valve for 2,869,793l/l959 Montgomery 241/ 186X choice between the functions. The hood isclosed by bolts held 3,202,369 8/1965 Judd 241/190 taut by wedges whichrest on surfaces sloping in a direction 3,283,698 1 1/ 1966 Williams100/95 such that vibration tends to tighten the wedges.

0 0 I3 I e 0 I9 E /a m m 7/ o if Z9 2 3545690 SHEET 1 BF 3 PATENTED DEC8 I976 I NVEN TORJ BY 019% WWW PATENTEB on: 8|976 HOOD SHEET 3 OF 3srmnnmm TYPE .HAMMERMILL INTRODUCTION The invention of which the presentdisclosure is offered for public dissemination in the event thatadequate patent protection can be given relates to hammermill typeshredders. The illustrated form of the invention is especially suitablefor shredding junked automobiles, only slightly stripped.

Hammermills have long been used for shredding scrap steel but are betterknown in other uses such as crushing rock, grinding grain etc. Heavyhammers along the periphery of a rotor are rotated at high speed, theirtips following a circular path known as the hammer circle. When a largepiece of scrap metal is fed into the hammer circle, it is struck byhammers which tear off small pieces. The hammers may also sweep or throwa larger piece along within a cage of grate bars within which the hammerrotor rotates. Pieces which are small enough may escape through thegrate openings, larger pieces being struck repeatedly until reduced tosize.

In a US. Pat. application being filed approximately concurrently byTheodore A. berhellmann, Ser. No. 575,335, now US. Pat. No. 3,489,078"certain features of the present preferred form of the invention arebeing claimed. The present application is directed toward the featuresof this preferred form of invention which may use, but which go beyond,the initial concepts which are the subject of the Oberhellmannapplication.

According to the present invention, improvements are made in the initialgrate structure with a view to quick discharge of abrasive particles andother advantages. In addition, an improved gravity-tightened wedgeclamping means is provided for holding the hood tightly closed. Alsosome improvements in the hydraulic system are provided, especially forgreater safety. j j

The rear end of the hammermill, opposite the feed end, is a hood whichmay be opened for servicing. Safety features and quick-release clampsare provided.

Additional objects and advantages of the invention will be apparent fromthe drawings and from the following description.

DESIGNATION OF FIGURES FIG. 1 is a perspective view of an embodiment ofthe invention chosen for illustration, including adjacent related parts.

FIG. 2 is a fragmentary view similar to a part of FIG. 1 but showing thehood of the hammermill raised for servicing.

FIG. 2A is a view of a wedge clamp for the hood.

FIG. 3 is a vertical sectional view through the hammermill, showing alsothe feeder.

FIG. 4 is an approximately horizontal sectional view through thehammermill of FIG. 3, without the feeder.

FIG. 5 is a hydraulic diagram for the hydraulic controls for the twopairs of hydrauliccylinders.

FIG. 6 is a'diagrammatic view of the feed roll drive.

semination is detailed to ensure adequacy and aid understanding, this isnot intended to-prejudice that purpose of a patent which .is to covereach new, inventive concept therein no matter how others may laterdisguise it by variations in form or additions or further improvements.The claims at the end hereof are intended as the chief aid toward thispurpose, as it is these that meet the requirement of pointing out theparts, improvements, or combinations in which the inventive concepts arefound. u 1

An embodiment of the invention is shown as a whole in FIG. I. A car body11 is placed on a feed chute 12 by a suitable lifting device such as agrapple I3, operated by cables 14, and controlled by a crane operator,-the crane not being shown. A feeder head 16, which includes a drivenroller as will be described, may be raised and lowered by a pair ofhydraulic cylinders 17 of which one is shown in FIG. 1. The raising andlowering and the drive of the feed roll may be controlled by an operatorin booth 18, who "may view the feeding operation through a window 19. Apowerful'motor in a motor shed 21 drives a shaft 22 on which the hammerrotor to be described is mounted. This hammer rotor is housed within thehousing or body 23 of the hammermill which rests on a concretefoundation 24. The foundation 24 has a passage through it in which adischarge conveyor 26 runs, being driven by a chain drive within theguard 27. The conveyor 26 dumps into a hopper 28 which discharges onto aconveyor 29, leading to the next unit of the plant.

The inside of the hammermill is made quite accessible by opening theupper rear portion or hood 31 of the hammermill housing, by means of apair of hydraulic cylinders 32, one of which is visible in FIGS. land 2.The hood 31 is shown in the raised or open position in FIG. 2. I

THE FEEDER As seen in FIG. 3 a feed roll 36 above the lower end of chute12, is driven by a motor 37, preferably at a controllable speed. Also,it is important to have 'means for raising and lowering the feed roll36, this means comprising hydraulic cylinders 17 which raise a feed rollframe 38 pivoted'to the chute at 39. Although the feed chute 12 is shownat a fairly steep pitch, this is primarily for the purpose of causingcar bodies or the like to slide down to the feed roll 36. Accordingly,the approach surfaces to feed roll 36 need not be so steep or need notbe inclined at all, if other meansis provided for moving the car bodiesto a position at which they will be controlled by feed roll 36,preferably providing some feeding force to aid the feed roll inadvancing the car bodies into the hammermill. This may be a vibratoryfeeder. The feed roll, according to one feature of the invention, can beraised to a point of sufficient clearance e.g. 4 inches) to receiveunder it the hood of an unflattened car body, is provided with aplurality of peglike pro jections 40' and can be powered downhydraulically.

The feed roll 36 functions not only to move the car bodies into thehammermill, flattening them at the same time, but also to prevent themfrom being dragged into the mill too fast by the rotating hammers 41 and42.

Y ROTOR, BREAKER BAR AND GRATES The hammers 41 and 42 are a part of arotor 40 carried and driven by shaft 22. More specifically, the hammers41 are carried by arms 43, and hammers 42 are carried by arms 44 whichare interspersed between arms 43 and extend perpendicularly to them.Preferrably the arms 43 and 44 are welded together, but in any eventthey are keyed to shaft 22 to be driven by it. The hammers 41 and 42 allswing on bolts 46. They tend to maintain the position shown in FIG. 3due to their centrifugal force, but will swing slightly from thisposition as they strike heavy objects and preferably can swing 360 aboutthe axes of hammerbolts 46.

The hammerbolts 46 are carried not only by the arms 43 or 44, but alsoby end disks 47, which are also keyed to shaft 22. End disks 47 rotatewithin side liners 48 which preferably provide a small clearance forrotation of disks 47. Shaft 22 is rotatably carried by sturdy bearingassemblies 49. According to common practice, all internal surfaces ofthe hammermill housing which would be subject to wear and abrasion areprotected by removable liners such as the liner 48.

A breaker bar or cutter bar 151 is positioned at the discharge end offeed chute I 1. Preferably this bar extends fairly close to the hammercircle. It is also preferred that the breaker bar 51 be provided withnotches 52 through which the hammers 41 swing. These notches separateprojecting teeth or tongues 53 on the breaker bar which are located inthe planes of rotation of the hammers 42. It will be observed that thehammers 42 have an effective length shorter than that of hammers 41. Bythis is meant that their outer tips are not as far from the axis ofshaft 22 as are the outer tips of hammers 41. It is desired that thelonger hammers 41 chop slugs out of an entering car body,

and that then the shorter hammers 42 chop off the intervening tongues.Cutter bar 51 rests on a table 54 on which it may slide. At present itsposition on table 54 is adjusted by screws 56 and the breaker bar isclamped in place by bolts 57. Adjustability is not believed to benecessary however, because when wear is excessive bar 51 is turned.Breaker bar 51 is preferably reversible, having notches 52 and tongues53 along the unused edge of the breaker bar, as seen at the lower rightin FIG. 4. Since also either face can be up, it has four wear surfaces.

A series of fixed grate bars 61 and 67 with discharge openings thereinextend around the rotor 40. The first of these openings is as close tothe breaker bar 51 as is practicable, separated only by a lower breakerbar 62, which is immediately adjacent a support wall 63 for breakertable 54. Each grate bar is supported only at its ends and hence itsmain body forms a sturdy beam. Each grate bar 61 has welded to it aseries of spacer blocks 64 which project inwardly to provide teeth 66which help shred the car bodies in case any large pieces escape thechopping action of the hammers on breaker bar 51. According to thepresent invention the spacers 64 also provide relatively narrow openingsto help release glass fragments and other abrasive dirt for immediatedischarge, aided by the tendency of such materials to explode on impact.

The second type of grate bar 67 begins approximately oneeighth of arevolution beyond the breaker bar 51. These bars 67 are cast ofmanganese steel with integral spacer lugs 68 and 68'. According to thepresent invention, the surfaces of bars 67 facing against the hammerrotation slope outwardly and rearwardly so that metal pieces whichstrike them will be deflected outwardly to escape quickly from thehammer action. The quick escape of metal pieces after they have beenreduced to size is desirable to reduce wear on the hammers and otherparts. The rearward faces of beams 69 slope somewhat outwardly andrearwardly also, but this is incidental to other considerations such asproviding adequate openings between the grate bars. However, with thesloping grate bars of the present invention, the openings are preferablysomewhat smaller than they might be with radially disposed grate bars,inasmuch as the sloping of the grate bars facilitates the passage of themetal pieces through the smaller openings. Hence, more or sturdier gratebars can be provided, with some reduction in the need for replacementdue to wear.

When hood 31 of the housing is swung open on its hinges 71, by hydrauliccylinders 32, worn bars 67 and 61 and lower breaker bar 62 may beremoved and replaced. Also access is given for easy replacement ofhammers or building them up with welding. Cutter bar 51 may be removedendwise (parallel to the rotor axis) for turning or replacement.

At the end of the series of grate bars 67, there is preferably providedan inwardly projecting deflector impact bar 72 which preferably has earswelded to it for securing by bolts 70. A substantial number of metalpieces which have not escaped the hammer area prior to reaching theimpact bar 72 will be deflected by it and ejected into the dischargearea 73. A reinforcing beam 74 is positioned above the cover plate 76 inthe vicinity most frequently struck by such pieces.

An additional removable breaker plate 77 is located in a position to bestruck by pieces passing the breaker plate 72. This breaker plate may bereplaced by being raised nearly vertically, after withdrawing onesecuring rod 78.

Feed roll 36 cannot only be raised and lowered as will be described, butalso it is driven at a variable speed which is subject to both manualand automatic control. So long as the rotor of the hammermill rotates atnearly full speed, the manual control of the drive of feed roll 36 willprevail. This speed is controlled by a knob 81 on the operator's panelin control booth 18. By experience, the operator will learn the mostdesirable speeds for different conditions of feed. Through a controlsystem 82, the speed of drive of roll 36 is controlled by variations inthe energization of a magnetic clutch 83 of eddy current type throughwhich motor 37 drives speed reduction gears 85, by which roll 36 isdriven. If the hammermill rotor encounters such heavy feeding that itsspeed is materially reduced, a current transformer 84 on one of the maincurrent supply lines to hammermill motor 86 will detect an increasedcurrent flow and cause control system 82 to reduce the speed of drive offeed roll 36, and if necessary, to stop this drive. The operator cancontrol the sensitivity with which the speed is reduced by adjusting aknob 87, which may be more remotely located, Another remote knob, notshown, can control the maximum speed attainable by knob 81. The mainportion of the control system 50 is 1, Louis Allis SCR Type MD-2controller.

Control systems of this type are old, and have been used previously incontrolling the feed to rock crushers. Accordingly, they need not bedescribed in detail. Here, however, feed roll 36, aided by gears 35 witha ratio of about 50 to l, additionally restrains the bodies from beingdrawn in too fast.

HYDRAULIC SYSTEM The preferred hydraulic system is shown in FIG. 5. Ahydraulic pump 91 is driven by a motor 92, with the usual gage, reliefvalve, etc. A manual valve 93 selectively connects pump pressure(through line 94) to either line 96 leading to the feed roll elevationcontrol or to line 97 leading to the control for swinging open the rearhousing portion or hood. in a third position valve 93 can connectpressure line 94 directly to return or discharge. The valve 93 is in thenature of a safety feature so that it will be impossible for theoperator to inadvertently elevate the hood and the feed roll at the sametime.

The line 96 leads to a second manual valve 98 which is the valve theoperator ordinarily operates for controlling the elevation of the feedroll 36. This valve has four positions. In the position shown the oil isordinarily locked in the cylinders 17 holding them at whatever positionthey are in. The pump pressure is bypassed to return. This is theposition to which the spool of the valve (which is connoted by theshowing 98) is spring biased. When the spool is moved in one direction,outwardly of the valve (downwardly in FIG. 6) the pump pressure line 96and the return line will be connected to the cylinders 17 in a directionto lower the roller 36. Oil pressure, varied with the amount of spoolmovement, can thus be added to the weight of the roller and the frame 38to help flatten or mash down a car body or to grip it more firmly forfeed. A gage 99 shows the amount of applied pressure.

When the spool of valve 98 is moved in the opposite direction, it.approaches a first position in which the pump pressure line 96 and thereturn line are connected oppositely to cylinders 17 so that the feedroll is raised. With movement of the spool beyond this position, the twoends of cylinders 17 are connected to each other so that the float"condition is achieved and, subject to the weight of roller 36 and itsframe 38, the roller 36 may rise and fall as may be determined by theforce exerted on it by a car body passing through. A weight 101 may beadded to give the desired amount of pressure on a car body in this floatcondition.

A relief valve 102 may be set to determine the maximum pump pressurewhich will be delivered to cylinders 17.

When the valve 98 is in its position of rest, the position at which thecylinders 17 are hydraulically locked, the feed roll 36 may neverthelessbe lowered by energizing a solenoid 103 to operate valve 104 to connectthe lower ends of cylinder 17 to discharge, a check valve 106 permittingthe upper ends of cylinder 17 to draw oil so that there will be nocavitation.

When the selector valve 93 is moved in the direction to permit raisingthe hood, control of the hood is achieved in much the same manner bymanual valve 111. However, in this instance, the float" position is notprovided. A relief valve 112 to be restrained so as not'to slam shut.Accordingly, a counterbalance valve or pilot valve 114 is provided. Whenthe spool of 111 is moved in the direction to apply pump pressure to theupper ends of cylinders 32 to lower the hood, and the hood passes thepoint at which it is balanced and begins to exert a pressure in theclosing direction, the counterbalance valve 114 will close the line fromthe bottom of cylinders 32, or partially close it to control the speed.Although the operation of such valves is well known, it may be explainedthat a spool represented by pointer 1 l6 prevents downward flow from theline 117 through line 118' to discharge line 119 except when apredetermined pressure is applied to the spool through line 121, knownas the pilot line. A suitable pressure for opening the connectionrepresented byarrow 1 16 is 200 pounds on the pilot line 121. Thus,whenvalve spool 111 is moved toward the position for lowering the hood,pump pressure is applied to line 122 leading to the upper ends ofcylinders 32. However, the cylinders cannot lower the hood until line117 is connected to discharge. Thisis accomplished as soon as thepressure in line 122 builds upjto'200 pounds by virtue of the pilot line121 which actuates the pilot or cushion valve 114 to make the connectionrepresented by swinging arrow 116 into alinement with connecting line118; For raising the hood, check valve 123 permits the pump pressure tobe delivered to line 117 regardless of the condition of the valverepresented by the arrow .1 16.

ADDITIONAL FEATURES AND FURTHER DISCLOSURE Most operators desire thehood31 to be securely fastened during operation. Heretofore, it has usuallybeen secured by a series of threaded screws or nuts and bolts which hadto be removed by the slow process of unscrewing. According to thepresent invention quick opening clamp means are provided. As seen inFIG. 2A, a headed bolt 126 is slipped through passages in support flange127 and flange 128, which is part of hood 31. A wedge 129 is slippedthrough a slot in stem 131 of bolt 126, and driven tight'so that itwedges flange 128 against flange 127. If bolt 126 is vertically arrangedas shown, there would be danger that vibration would loosen the wedge129. This loosening is avoided by providing a sloping seat 132 for wedge129, so that (under the influence of gravity and vibration) wedge 129tends to move downwardly to the right, as seen in FIG. 2A so as tomaintain itself in wedging position. At locations where the bolt 126 ishorizontally disposed the pin 129 will be inserted, downwardly and theseat 132 is not needed. In either event, the end of the slot in stem 131will be shaped to engage full face against the side of the wedge 129.Where the seat 132 is provided it has an aperture through which stem 131passes as it is inserted through flanges 127 and 128.

Fabricated grate bars 61 and breaker bar or cutter bar 51 are preferablyformed of a very hard steel alloy of an abrasion resistant class such asthe US. Steel T-l class, quenched and tempered. At present, a 321minimum Brinnel hardness is specified. Because the more abrasivematerials, such as glass fragments, are usually discharged through thefirst grate section (bars 61) the following bars 67 need not be as hard,although they may work-harden.

The teeth 53 of cutter bar 51 present a severe problem in resistingbending and wear. In the present use they should not be less than 3inches in width, 2% inches having been known to bend laterally. Assumingthat a thickness is chosen suitable for the job they should besubstantially as wide as their thickness. For the teeth 53 to be 3inches, or the preferred 4% inches wide, it follows that the hammers 41must be spaced still further apart. It is partly because of this widespacing of the hammers 41 that a second set of interspersed hammers 42is desired. The teeth should not be too long, 3% inches having beenfound to be satisfactory at least when reinforced along part of theirlength by resting on the table 54.

Although there might seem to be danger of breakage of the teeth if theywere made too hard, it has been found that the increased surfacehardening resulting from torchcutting of bar 51 without subsequenttempering does not cause breakage, and reduces wear. 1

In one metal shredder according to the present invention the maximumspeed of the feed roll 36 is set at about 55 peripheral feet per minute.A speed over 50 is rarely used, however, while the shredding is takingplace. The rotor speed in that machine is 720 r.p.m. Theoretically,these comparative speeds would result in nipping the steel successivelywith such slight movements between nips that the desired action ofchopping off slugs of moderate size would not be achieved. However, forsome reason the theoretical action of merely nipping off toothpick likepieces does not occur. This is probably because the hammers, as theystrike the metal are moving in a'direction to seize the metal and drawit inwardly somewhat. Because of the tendency of the hammers to draw themetal in, it is important that the feed roller 36 be capable ofrestraining the metal, so as not to overload the hammermill.

A 2,000 horsepower motor is preferred for driving the rotor 40, assumingthe rotor to have a 74 inch outer hammer circle and to be 1 12 incheslong, measured from the outside faces of the disks 47. Much higherhorsepower motors have been used heretofore for shredders of comparableoutput. As a matter of fact, an even smaller motor, 1,500 horsepower hasbeen used successfully with the present machine.

ACHIEVEMENT In this field in which motors capable of deliveringthousands of horsepower have been required, substantial savings of poweruse and motor size have been made. Wear has also been reduced. Ofcourse, wear is inevitable on the cutter bar, the hammers and the gratebar's, but'the cutter bar may easily be turned to present successivelyfour faces to wear, and replacement of the others is made easy by thehydraulic opening of the hood 31 and by quick opening clamps.

Car bodies with frames and axles and which have not been previouslyflattened can be drawn into the machine, and simultaneouslyprogressively flattened or mashed down, by the driven and power-loweredfeed and compressions roll. Because of its restraining action andpartially automatic control of its speed, the bodies can be fed at agood speed without danger of overloading the hammermill.

In addition to making valuable scrap metal from junk which is mostlysteel, such as car bodies, the present invention is useful in disposalof solid waste, such as the contents of city dumps, rubble from wreckageof buildings in which metal is often encountered, and the like. Ofcourse, the feed roll clearance will usually not need to be as large forsuch uses, and some uses of some features of the invention may not needthe feed roll at all or may use it differently located.

We claim:

1. Apparatus for shredding metal including a feeder for feeding metal tobe shredded at a controlled speed with restraining action on the metal,and a hammermill for receiving the metal fed by the feeder; saidharm'nermill including:

a cutter bar over which the metal is fed, a grate cage extendinginitially downwardly and generally arcuately from said cutter bar, and adriven rotor having hammers thereon, rotating within the curvature ofsaid cage with its axis so positioned that the hammers move close to thecutter bar and across the direction of entry of metal into thehammermill to chop pieces from it;

said cutter bar having a series of notches therein opening toward therotor and said rotor having one set of hammers disposed to pass throughsaid notches, and another set of hammers terminating closer to the rotoraxis and disposed axially between the hammers of the first set tocooperate with the portions of the cutter bar between the notchesthereof; and

the grate cage having a seriesof relatively small discharge openingsextending from substantially adjacent the cutter bar in the direction ofrotor rotation to discharge abrasive particles, and a series of 'largeropenings extending therefrom to a point in which the radial dischargedirection is steeply upward, surfaces of this latter series which faceagainst the direction of rotation sloping outwardly and in the directionof rotation to deflect outwardly metal pieces su'iking said surfaces.

2. Apparatus for shredding metal, including feeding means for feedingscrap metal at a controlled speed and restraining it against being drawnin at higher speed, rotor means carrying a plurality of swing hammers,cutter bar means extending parallel to the axis of said rotor means andcooperating with said hammers to break up the scrap metal, and a gratepartially surrounding said rotor means; said grate comprising:

a first portion beyond said cutter bar including a plurality ofrelatively closely spaced and parallel bars, each extending generallyparallel with said axis, spacer means between said bars for maintainingsame in spaced relationship, said spacer means including toothed meansprojecting inwardly of said bars toward said rotor means to aid in thequick release of brittle inclusions in said scrap and their dischargethrough said first portion; and

a plurality of relatively widely spaced-apart bars forming a secondgrate portion beyond said first grate portion, each of said secondplurality also extending parallel to said axis.

3. Apparatus for shredding metal as set forth in claim 2, wherein thebars in said second grate portion form discharge openings slopingoutwardly and in the direction of rotor rotation to facilitate dischargeof said scrap and reduce wear thereof.

4. Apparatus for shredding metal including a feeder for feeding metal tobe shredded, and a hammermill for receiving the metal fed by the feeder;said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generallyarcuately from said cutter bar, and a driven rotor having hammersthereon, rotating within the curvature of said cage with its axis sopositioned that the hammers move close to the cutter bar and across thedirection of entry of metal into the hammermill to chop-tear pieces fromit;

said cutter bar being removable endwise and insertable in each of fourpositions to present different wear surfaces toward the hammer approach,said grate cage being formed of separate bars slidable about the rotoraxis to a point of removal, the hammermill including a hood hinged togive access to the point of removal; and

hydraulic means for raising the hood and wedge-type quickopening clampsfor securing the hood in its closed position, at least one of saidclamps including a vertically extending bolt, a wedge drawing said boltinto position, and a seat on which said wedge rests and slides, saidseat sloping in a direction to gravitationally bias said wedge in thewedging direction.

5. Apparatus for shredding metal including a feeder for feeding metal tobe shredded, and a hammermill for receiving the metal fed by the feeder;said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generallyarcuately from said cutter bar, and a driven rotor having hammersthereon, rotating within the curvature of said cage with its axis sopositioned that the harnmers move close to the cutter bar and across thedirection of entry of metal into the hammermill to chop-tear pieces fromit;

said grate cage being formed of separate bars slidable about the rotoraxis to a point of removal, the hammermill including a hood hinged togive access to the point of removal; and

hydraulic means for raising the hood and wedge-type quickopening clampsfor securing the hood in its closed position, at least one of saidclamps including a vertically extending bolt, a wedge drawing said boltinto position, and a seat on which said wedge rests and slides, saidseat sloping in a direction to gravitationally bias said wedge in thewedging direction.

6. Apparatus for shredding metal including a hammermill having an accesshood, adriven feed and crushing unit for feeding metal to thehammermill, and a hydraulic system for raising and lowering the hood andfor raising and lowering the feed unit, including a pump for providingpump pressure, first and second hydraulic actuators for the feed unitand hood respectively, first and second manual control valves for thefirst and second actuators, and a selection valve for connecting thehydraulic pressure selectively to one only of first and second manualcontrol valves.

7. Apparatus for shredding metal according to claim 6, including anadditional valve for at-will lowering the feed roll independently of theselection valve.

8. Apparatus for shredding metal including a feeder for feeding metal tobe shredded, and a hammermill for receiving the metal fed by the feeder;said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generallyarcuately from said cutter bar, and a driven rotor having hammersthereon, rotating within the curvature of said cage with its axis sopositioned that the hammers move close to the cutter bar and across thedirection of entry of metal into the hammermill to chop-tear pieces fromit;

said grate cage including separate bars slidable about the rotor axis toa point of removal, the hammermill including a hood hinged to giveaccess to the point of removal and swingable about the hinge across aposition of dead center balance; and

hydraulic means for raising the hood and wedge-type quickopening clampsfor securing the hood in its closed position, at least one of saidclamps including: a vertically extending bolt, a wedge drawing said boltinto position, and a seat on which said wedge rests and slides, saidseat sloping in a direction to gravitationally bias said wedge in thewedging direction.

9. Apparatus for shredding metal including a hammermill having an accesshood, a driven feed and crushing unit for feeding metal to thehammermill, and a hydraulic system for raising and lowering the hood andfor raising and lowering the feed unit, including a pump for providingpump pressure, first and second hydraulic actuators for the feed unitand hood respectively, first and second manual control valves for thefirst and second actuators, and a selection valve for connecting thehydraulic pressure selectively to one only of first and second manualcontrol valves; and quick opening clamps for securing the hood in itsclosed position, at least one of said clamps including a verticallyextending bolt, a wedge drawing said bolt into position, and a seat onwhich said wedge rests and slides, said seat sloping in a direction togravitationally bias said wedge in the wedging direction.

10. Apparatus for shredding large metal objects such as automobilebodies, including a rotor having swing hammers thereon, feed meanspositioned generally to one side of the rotor, a housing enclosing therotor, opening on the forward side to the feed means, and having arcuatechannels extending along the hammer circle of the rotor approximatelyfrom the feed means around rearwardly of the rotor approximately to ahorizontal plane through the axis of the rotor, grate bars carried insaid channels and removable rearwardly of the rotor, the portion of saidhousing above said plane and rearwardly of the rotor comprising a hoodhinged approximately along one edge thereof to be opened for exposingthe rotor and channels; said feed means including active portions whichcan be raised and lowered, hydraulic cylinder means for actuating saidactive portions, double acting hydraulic cylinder means for the hood, asource of hydraulic fluid under pressure, and valve means forselectively controlling hydraulic flow to the first mentioned or lastmentioned cylinders.

l 1. Apparatus for shredding metal according to claim 10 in which thehood, in opening, swings past a dead center balanced position wherebyits being maintained open is independent of maintaining hydraulicpressure.

12. Apparatus for shredding metal including a feeder for feeding metalto be shredded, and a hammermill for receiving the metal fed by thefeeder; said hammermill including:

a cutter bar, a grate cage extending initially downwardly and generallyarcuately from said cutter bar, and a driven rotor having hammersthereon, rotating within the curvature of said cage with its axis sopositioned that the hammers move close to the cutter bar and across thedirection of entry of metal into the hammerrnill to chop-tear piecesfrom it;

said grate cage including separate bars slidable about the rotor axis toa point of removal, the hammermill including a hood hinged to giveaccess to the point of removal and 10 swingable about the hinge across aposition of dead center balance;

hydraulic means for raising the hood and wedge-type quickopening clampsfor securing the hood in its closed position, at least one of saidclamps including:

a vertically extending bolt, a wedge drawing said bolt into position,and a seat on which said wedge rests and slides, said seat sloping in adirection to gravitationally bias said wedge in the wedging direction;and

the cage including grate bars along the rear upper quadrant of the rotorcarried by the hood and moved with it.

13. Apparatus for shredding metal including a hammermill having anaccess hood, a driven feed and crushing unit for feeding metal to thehammermill, and a hydraulic system for raising and lowering the hood andfor raising and lowering the feed unit, including a pump for providingpump pressure, first and second hydraulic actuators for the feed unitand hood respectively, first and second manual control valves for thefirst and second actuators, and a selection valve for connecting thehydraulic pressure selectively to one only of first and second manualcontrol valves; the hydraulic actuator for the hood being double actingcylinder means; and said hood swinging across a dead center balancedposition to be stable in either open or closed position independently ofhydraulic pressure.

